Self‐Healing Cellulose‐Based Biopolymer Electrolytes Plasticized With a Biodegradable Protic Ionic Liquid: Toward Sustainable Lithium‐Ion Batteries

ABSTRACT The lithium‐ion battery (LIB) market continues to expand and must now meet increasingly stringent regulatory sustainability requirements. To mitigate the impact of petrochemical‐derived polymer electrolytes, bio‐sourced polymers have attracted intense interest. In the present work two cellulose derivatives, methyl cellulose (MC) and cellulose acetate butyrate (CAB), were doped with lithium perchlorate (LiClO 4 ) and plasticized with ethylammonium nitrate (EAN), a biodegradable protic ionic liquid synthesized in‐house, to give free‐standing, intrinsically self‐healing biopolymer electrolytes (BPEs). All EAN‐plasticized membranes exceed the 10 −5 S cm −1 threshold conventionally required of a battery separator‐electrolyte. The best membrane, B(MC‐IL)0.2, delivers an ionic conductivity of 6.84 × 10 −4 S cm −1 at room temperature; and investigation on placticized membrane with higher proportion (05 wt%: B(MC‐IL)0.5) shows some changes on membrane surface, affecting the SEI, thus the conductivity of the membrane (5.45 × 10 −4 S cm −1 , RT). An operationally defined electrochemical stability window of 4.4 ± [0.2] V vs. Li + /Li is obtained by linear sweep voltammetry. An optical healing efficiency of ∼99% is reached after 3 h at 60°C, and recovery of some relevant functions of the membranes are assessed by impedance spectroscopy and tensile testing before damage and after healing.